The present invention relates to assembly apparatus for lead-acid batteries, and, more particularly, to welding apparatus for connecting battery elements in a through-the-partition fashion.
Lead-acid storage batteries are well known and generally consist of a series of cells, usually three or six, connected in series to provide the desired voltage output. Six cell, lead-acid batteries are used extensively for automobiles, often being termed "SLI" (starting, lighting and ignition) batteries.
Over the years, many configurations have been suggested for connecting adjacent cells in such batteries. At present, the construction most typically used involves making such connections in a through-the-partition fashion. U.S. Pat. No. 3,313,658 to Sabatino et al. and U.S. Pat. No. 4,013,864 to Tiegel et al. are examples of prior methods and apparatus for effecting such connections. Such apparatus is designed to make the necessary intercell connections in the conventional battery constructions, viz.--in which only a single connection is needed through each cell partition.
However, the battery industry is continually being faced with seemingly ever-increasing demands. There is accordingly considerable pressure on automobile manufacturers to provide improved performance, e.g.--better gas mileage; and this translates to efforts to reduce the overall weight of the automobile as much as possible. Lighter weight batteries are likewise being required so as to contribute to weight reductions. Similarly, there is a tendency for requiring a smaller-sized battery, simply due to the amount of space available under the automobile hood.
At the same time, the number of smaller-sized automobiles with smaller engines currently in service has risen dramatically. While the batteries used for such smaller automobiles can be smaller, the designs required need to be more efficient. Thus, for example, reducing a 350 cubic inch engine to one-half that size does not allow reducing the battery performance requirements to the same extent. The starting or cranking power, as one example, which is required for such a smaller engine, is thus more than one-half the requirement for the 350 cubic inch engine. Moreover, four cylinder engines require a substantially higher cranking speed to obtain engine starting. Indeed, some four cylinder engines require up to one and one-half to three times the cranking speeds of V8 engines.
The increase in popularity of diesel-powered automobiles has also contributed to the demand for more efficient batteries. Engines of this type thus require more starting power than a comparably sized gasoline-powered engine. As a result, it is not unusual to see a diesel-powered automobile employ two batteries in parallel or utilize an extremely large battery, almost approaching a truck battery size.
These and other considerations dictate that battery manufacturers provide a battery with substantially improved performance characteristics. The co-pending Klang et al. application identified herein describes a battery having exceptionally high power characteristics per unit weight or volume in relation to commercially available maintenance-free and other SLI batteries.
The type of battery described in the Klang et al. application readily lends itself to production on a large scale, high volume basis. However, the commercially available, intercell welding apparatuses cannot be used for welding the connections in such batteries without some modification. First of all, in embodiments of such batteries wherein the power characteristics per unit weight or volume are optimized, there will generally be considerable variation in size and mass from that of conventional battery components, such as, for example, the size and mass of the battery plates as well as the total top lead weight, viz.--the weight of the straps and terminals. As an example, the top lead in the Klang et al. batteries may be reduced to about 75% or so of that used in conventional batteries. This generally means that the mass of the strap is much smaller than is conventionally used, as are the strap projections (often termed "lugs" or "tombstones") which are fused to provide the through-the-partition intercell connections. Modifications in conventional welding apparatus to satisfactorily weld such smaller lugs or projections are thus required.
Moreover, and importantly, the Klang et al. batteries include multiple intercell connections, as opposed to the single intercell connection commonly used in conventional battery designs. In the Klang et al. batteries, at least two intercell connections are employed, often three or even perhaps four or more such connections being desirable. When three such connections are employed for example, this increases the number of welds from the five needed in a conventionally designed battery to fifteen such connections. Also, after the initial intercell connection is made through a particular cell partition, alternate current paths will be developed in the welding procedure which can adversely affect the desired characteristics of the weld.
It is also desirable in automating such production to provide speeds which are generally commensurate with the speed at which other assembly operations can be carried out. For example, plastic battery assembly lines for sealing the cover of a battery to the container can process one battery every 20 seconds or so. So as to provide satisfactory production rates, it is useful to provide a welding apparatus capable of achieving such production rates as well.